Tag Archives: geophysics

After a decade of dreaming and years of planning our team of 40 data-hungry geoscientists were given the scent and released from their cages (~desks) with the audacious task of blitzing the whole ice sheet to find samples for dating its retreat. This started in November 2012 in a grey drizzle at Seisdon sand and gravel quarry near Stourport and finished 09:30am 1st August 2015 in bright sunshine when we extracted our last sample, a seafloor core, from the Cleaver Bank in the southern North Sea. It really has been an epic two and half years witnessing the Terrestrial Team with sun-cream in the Scilly Isles to shivers in Shetland, and with dressing gowns in Donegal to JCBs in Norfolk. We really did covered the ground from south to north and east to west and snuck in 28 – yes 28 – different islands of Britain and Ireland, including Scilly Rock and Foula. When samples were not easy to spot and grab, we used radar, seismics and some occasional guesses to work out where to dig with shovel or digger or to core the hidden sediments. It is not quite true that no stone was left unturned, but I have been amazed at how close we got to that, thanks to some amazing levels of energy and motivation; it is indeed lucky that our team displayed traits of obsessiveness and kleptomania when it came to sampling. Bloody well done to all.

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So our very last sample (core 179-VC) on BRITICE-CHRONO has now been collected, marking the end of Cruise Two on RRS James Cook. Even though we never got to shout ‘One hundred and …eighty’ it is more than we had planned. We have sailed, steamed, or dieseled 8971.65 kilometres, taking in Skye, Rona, Shetland, and more North Sea banks including (the infamous Dogger) that you could shake a stick at. We have sampled deep (525 m) and very shallow (19 m), and calm and troubled (force 7). Our ship-track might look erratic to some but, as they say in marketing non-speak, it comprises a subtle blend of caution and well-planned targets with a hint of adventure and wild abandon yielding a truly inspiring collection of mud and sand to sate the yearnings of the most inquisitive discerners of ice sheet curios.

The loot under the care of Team Marine (Lou and Margot)

The haul, now sat in our refrigerated lorry-container and packed in plastic tubes was obtained by lowering our vibro- and piston corers through 18,891.4 metres of seawater and extracting over half a kilometre of sediment (Rich says 542.4 m). As well-known, of course, it is not the length that counts, but the quality. It will be some time however before we know which cores, places and transects yield the best shells and forams for dating, but Margot and Lou have already bagged, sifted and labelled the celebrity shells which we think have the best stories to tell….’well there was this bloomin’ huge great wall of ice that kept crashing down, and would you believe what happened next….’.

Science crew of the RRS James Cook cruise JC123

Thanks to Colm and his science team, the Captain and crew and the geological survey coring teams, and the weather, some good planning, crazy hunches and some luck, this scientific cruise has been a great and enjoyable success. We have a mammoth payload that we hope will provide a legacy of new information for decades. It has been a pleasure having Alex, the ever-present black ninja-photographer on-board, – he stalks, clicks and then runs – in his quest to document our highs, lows and silly moments. Hopefully you have already seen much of his work.

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We set out to do 50 years work in five. Taking this cruise with last year’s, which circumnavigated Ireland, along with our >300 person-days of terrestrial fieldwork we have bagged around 15 tonnes of samples for dating and I hope you agree that we have been around a bit. Sorry if we missed your patch, why don’t you have a go? It is an end of an era for our sampling effort. As project leader, I now breathe a large sigh of relief that it is over and has gone so well, phew and phew again. There is a tinge of sadness though, that we all feel as the fun, bonhomie and making of new friends on hard-won field exploits has now ended. No more pie shops or sneaky pints. Team Terrestrial (Rich and his gang) and Colm’s Marine Crew, can now stand-down to great applause. Derek’s Geochron Team have their work cut out to carefully analyse all the samples and then our Transect Leaders (Tom, Dave, Rich, James, Colm, and Sara) will rise to the challenge of making sense of it all and telling us the story that the shell started to blurt out.

Taking things one day at a time

Chris Clark, signing off on behalf of BRITICE-CHRONO, currently steaming 11 knots, homeward bound, over the Tea Kettle Bank of the southern North Sea. All cores logged and packed and the pinging geophysics finally turned off.

Darkness. A great mass of ice overhead. The eerie rumbling of a large, uncompromising mass, slowly but steadily on the move. Below a thick layer of stiff red sediment, ground off the red bedrock, crushed and churned into a lumpy, sticky blanket of glacial till.

Dark coasts

What would later be called Cape Wrath was only miles to the south, but there was no cape yet. Just the grinding of slow and unforgiving ice moving north into the North Atlantic. But the times were changing. The sun gained in strength, atmosphere and ocean started to warm and the gigantic ice mass, later to be known as the British-Irish Ice Sheet, was in decline. As its surface melted, more water reached its bed, and it began to slide helplessly over its own sediments. Slowly it thinned, and retreated in the direction of the Scottish mountains with the ocean lapping relentlessly at its edges.

There seemed to be no hope, but the ice sheet made one last bold dash towards the edge of the continental shelf before it faltered. The recently deglaciated seabed and freshly deposited grey ocean sediments were bulldozed and overrun again by ice on the move, and buried once more in a blanket of red till. Linear ridges (moraines) marked the limit of this temporary re-advance. But it was only a death throw; the re-advance didn’t get far. The ice sheet’s days were numbered. The advance stopped, and turned into irreversible retreat.

A geophysical search for the perfect core…….

Against a backdrop of rumbling, calving icebergs, station JC123-048VC slowly became ice free, as the snout of the ice sheet moved back over the site. A cold, shallow sea took its place; first, still close to the snout of the ice sheet, where streams of meltwater rushing into the waiting sea water lay down a blanket of coarse sand. As the ice retreated further, taking the meltwater streams with it, the sea fell silent. Only fine sediments spat out into suspension by the dying ice sheet made it to our site, slowly covering it in a thick, grey blanket.

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The ice sheet sent a final message as the ice margins retreated south towards the land; a message from an iceberg. As it passed, melting, overhead of station JC123-048VC, pebbles slipped from its icy grip. They plummeted into the depths, impacting into the soft fine clay sea bed. As soon as this excitement started it was over, and the pebbles were slowly covered by more of the same grey clay.

With the great weight of the ice gone, the Earth’s crust rose like an ancient giant from its slumbers, pushing the Scottish continental shelf closer to the sea surface. Over time, the waters shallowed, and the seabed currents became stronger. The last vestiges of the glacial seafloor were scoured by contour currents, which deposited the spoils of an energetic coast on the eroded sediment below. Millennia later coarse sand and shell debris formed a layer of several inches thick. And then on Sunday the 12th July 2015 all changed.

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There was an unfamiliar thud, and then the uncanny sensation of a vibrating tube burrowing into the sediment from above. It cut through the sand in a jiffy, passed the pebbles, and into the soft clays. The tube slid through it like a hot knife through butter. No struggle with the coarse sands lain down by meltwater streams either, only slowing on reaching the stiff, red till. It battled its way into it for a meter and a half. Then the friction became too much. The vibrocorer stopped, and then the whole tube, now full of sediment, was pulled back up to the sea surface, and hoisted back up onto the deck of the RRS James Cook, the ship it had come from. Peace returned once again on to the sea floor, at core site VC123-048VC, a few miles north of Cape Wrath, on the northwestern edge of Scotland; a land mass now devoid of ice sheets and glaciers.

The core came on board and was cut into sections, labelled, scanned, and split. Finally, we, the scientists who had planned the project, planned the cruise, sailed all the way from Southampton to Cape Wrath, and waited for the British Geological Survey (BGS) to deliver the core, first laid eyes on the sediment. The story was there: a stiff basal till deposited beneath the ice sheet; fines marking the first incursion of the sea; further glacial till documenting the ice re-advance, meltwater stream sediments deposited in front of the retreating ice margin; the fine clays deposited when the ice began to recede southwards containing drop-stones from the icebergs, and the marine sand of the modern seafloor. That was what we had come for. And this was the 48th core; none of the previous 47 had told the story of the vanishing British ice quite this clearly.

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Hopefully we’ll be getting more cores like this in the coming three weeks of the cruise. We need this story told in every sector of the British-Irish continental shelf. Only then will we have what we set out for: the complete saga of the Last British-Irish Ice Sheet.

Take some of the ‘finest’ brains in the country. Put them on a state-of-the-art research vessel which is filled to the brim with geophysical equipment, and has its own core scanning lab. Imagine what one could do with that! And what do we do with it? What is the scientific treasure we hunt? Mud. Six weeks at sea for mud (occasionally sand…)? We’ll be scrutinising it for years to come! Without mud the whole endeavour would be a failure; the mud must be treasured, cared for. It is the sedimentary archive that could answer the question of when and how the British-Irish Ice Sheet vanished. It is the wet lab coring teams that handle, care for and love the mud. There are two shifts: the Night-watch from midnight to noon, and the Day-team from noon to midnight. Whilst in the lab and, more importantly, out on deck, these have to wear armour: PPE (Personnel Protective Equipment) – a hard hat, hobnailed boots and some rather unflattering (generally oversized) overalls. The overalls are optional, but a sensible option at that; the job is a messy one, so unless you have an endless supply of clothes…. As the British Geological Survey (BGS) core team recover the mud to deck we have to wait – impatiently. How much have we recovered, and is it the right stuff? Even before the barrel is laid down we swarm expectantly around its end to get the first glimpse (and touch) of the treasure. The strength of the mud gives us so much information; we prod it, taste it…. Does it feel like silt, sand, clay; is it stiffened, reflecting the weight of former ice sheet bearing down on it? We recover everything from the core shoe, the core catcher; whatever sticks or falls out of the liner gets bagged, labelled, photographed and stored cool. But what is inside the liner is what we really want, it contains the story of the ice coming and going from the waters around these islands.

Heave

Ho

The liners are not easily released from the barrel; muscles are needed to get it out, and a tug-of-war ensues of scientists, BGS engineers, crew, random passers-by, anyone versus the barrel. But once the liner is out, it’s ours. The muds we desire are only useful if we know exactly where they are from, so labelling is everything. Every single core section has its own unique label, which will end up on its liner, caps, wrapping material, and the box it’s stored in. There are yellow caps for the tops and black for the base of each segment; which way is up matters! And that is only the beginning; there is no such thing as over-labelling, and that holds for cores sections, record sheets, scanned records, spreadsheets, photographs……

Lou: “The day shift consists of Steve, Zoe, Catriona, Kevin and me. Whilst Colm and Katrien spend the day planning where we will core next, we collect and process the cores. Generally our day starts at 11:20 with breakfast, which also happens to be lunch for the other crew members. Breakfast can be anything from a curry to fish and chips. Today’s option was Thai fish cakes, with noodles and sweet chilli sauce. Although having such a large meal first thing was rather odd to begin with, six weeks in it seems quite normal and a bowl of cereal would now disappoint. Shift begins with the midday handover meeting and our goodnights to the night team.

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Then work begins! We spend most of our shift either out on deck collecting and cutting the cores, or in the wet lab splitting, logging and packing the cores away with a constant dual stream of material either from the deep or from the MSCL cave. Frequently we split over 20 sections during our shift, and often it’s more than 25. Each section is 1 m long with each 1 m weighing between 10-12 kg, so after 12 hours of carrying, splitting, logging and packing it is a good workout. So the coring job may seem rather unglamorous and exceptionally mucky, and involves hard manual labour; it is also an exciting and rewarding part of the cruise. The sub-bottom profiles and bathymetry data provides a tantalising look at what might lie beneath, but it is only when the core is taken and the material viewed that you know whether or not we have captured the right material needed for the project, and whether there is something we can use for dating. Sometimes we are disappointed normally if we fail to guess correctly in the ‘guess-the-core-length’ sweepstake (Steve is slightly in the lead at the moment), but when a good core is opened, it changes the mood of everyone involved.

Our work still isn’t quite complete, cleaning and maintaining the lab ready for the night team, labelling, cropping and archiving all photographs, and Zoe dutifully scans all of the deck sheets. At midnight the night team relieves us and then we head either straight to bed or take a detour past the kitchen to get a post shift snack. A day shift favourite is Nutella (somewhere in the multi-verse other nutty spreads might exist) on toast. It is hungry work, coring!”

Margot: “the Nightwatch consists of Kasper, Riccardo, Jenny, myself and occasionally Richard (if he can drag himself away from the Geophysics, picking core sites and mostly chatting on deck). As we start our shift, we tend to find ourselves in the middle of a coring transect that has been planned before, so we of the night often start our shift on station, vibrocoring. We’ve discovered that Riccardo has a special talent for working hard but still staying clean, while Richard has the useful talent for removing almost any sediment from an unwilling core catcher. Kasper’s Danish (or Viking) muscles come in handy for removing the liner from the barrel, and Jenny has useful BGS contacts (which saves us, for instance, from running out of sample bags). I myself have developed the modest knack of writing upside down, for liner labelling purposes.

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Splitting and description has to wait until we receive cores from Elke and the core scanner cave, and she works 6AM to 6PM. The early part of the shift can be quite calm, if the core stations we have picked are far apart. Quite often nature festoons such a quiet early part of the shift with an amazing sunrise. The pace picks up dramatically as the cores start to emerge from the MSCL cave. It can get a bit hectic if we’re busily splitting and describing, interrupted by receiving new cores from the seabed. Core sections everywhere! But the splitting is exciting, as we get to see the whole sedimentary sequence for the first time. Do we have the ideal core, which consists of a subglacial till at the bottom, conformably overlain by marine sediments deposited after the ice retreated? Are there perhaps some nice shells in it for radiocarbon dating? When we see something we could use for 14C dating, we take it out. As we are coring, we have a competition running: guess the core length. It is very tight at the moment; Riccardo is in the lead, closely followed by Jenny, and Richard is trailing miles behind, but it all can still change, even with only two days to go. Eventually noon arrives, when we hand over to the day team, and then plonk down tiredly for lunch, which, for us, is more like late supper. After lunch and a cup of tea it’s bedtime! And then at around 11PM (ish) we get up again, and the sequence repeats.”

Treasure…..

As we both write this, the 212th core has been recovered from the large moraine in outer Galway Bay. There is some 6 tonnes of mostly mud in our refrigerated container, and we have picked more than 100 shells for dating. But we know exactly where every kilo came from, what it looks like, and which ones we want to target for further research. When we get back on land, we can hit the ground running…..

Leaving the Celtic Sea and the delights of the Celtic Deep, noon on Sunday 27th July, the Royal Research Ship (RRS) James Cook homed in on Britice-Chrono Transect 3 and the delights of the Irish Sea. For me work levels already high increased, with Transect leader duties to fulfil, and the challenges of finding till – glacimarine mud contacts throughout the sector, and do not forget the shells/fossils for the critical dating targets. That said without Katrien’s (van Landeghem) constant input and support it would have been ridiculous, the work in advance of the cruise identifying targets and new locations drew on considerable effort and collaboration focused on this marine sector of T3 over the past 2-3 years. The success of the efforts for T3 obviously relied on the excellent work effort, diligence and company of the cruise team, science crew, BGS and NOC Piston coring teams and the RRS James Cook captain and crew, all whom did everything they could to help us. Not singling people out, but I thank Katrien for constant input, advice and support as co-leader on this transect and Colm as Science Lead on JC106 cruise.

In the Celtic Sea, the ship was home to the friendly academic interplay between James and Daniel, the Irish Sea also offered up a number of longer standing and perhaps more vociferous historical debates! Understanding and interpretation of the nature and extent of glacimarine conditions in the Irish Sea basin has ebbed and flowed for 4-5 decades, with some proponents holding for a full glacimarine ice margin, others subaqueous margins with more restricted access to the ocean and the other end member glacilacustrine basins separated from the sea. For all these views a comprehensive borehole and geophysical survey targeting environments across the sea floor had the potential to advance understanding, but for Britice-Chrono we clearly needed glacimarine conditions and sediments to provide the marine shells and microorganisms that we can radiocarbon date to gain a chronology for retreat of ice from the basin. Marine fossils have been recovered from coastal glacigenic sediment sequences surrounding the Irish Sea for centuries, but debate continues over whether they are in situ or derived, eroded from the sea floor, during ice advance and then redeposited in glacial sediment. If in situ they offer the potential to constrain retreat of ice margins and the development of glacimarine conditions, if derived they cannot really advance our dating control. Some challenging fieldwork and some painstaking analysis of the fossils and microfossils lies ahead.

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Our journey from the Celtic Deep ~ 51°25’N to our first survey and core sites west of Anglesey around 53°15’N took just over 12 hours at a steady ~10 knots. Our first sites, a bit of a late addition and product of general brain-storming, were ~ 13-14 miles west of Holyhead and targeted the deep waters of northern extensions of St Georges Channel. The location kind of bridges T4 and T3, and we wanted some indication of deglaciation of the deep waters between Holyhead and Dublin. On reflection I was not sure what to expect here, but we had planned a sub-bottom profiler SBP and multibeam survey line as an initial exploration, but circumstances and our temperamental SBP conspired against us. The multibeam data on the other hand were excellent, it was a decent trough 2 miles wide 30-40m deep and we used the multibeam to avoid surface sand waves. Our aims were to avoid surface sand and access the underlying laminated glacimarine units, 2.5 hours and two vibrocores later, some success >3m of mud ending in reddish (an Irish Sea glacial signature!) stiff muds. These laminated or bedded sediments hopefully were lain down under marine conditions fronting the ice sheet as the ice margin retreated to higher ground east and north between Anglesey and the Isle of Man.

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From noon 28th July we moved east and north between the Isle of Man and North Wales, and into a region a large part for me where my interest in this research started, working for and collaborating with Geoff Thomas on sections and sediment all around the Irish Sea. In the deeper waters between the Isle of Man and North Wales, our multibeam data gave us a view onto a very well preserved glacial landscape of drumlins and flutes, moulded elongate low hills shaped by the passage of ice. Uncovered as ice melted and then preserved beneath water probably ever since, their summits are grooved with markings probably formed by ice-bergs calving from and then grounding on the landform surface fronting this glacier. Guided by the multibeam sea floor topography and our shallow geophysical data we targeted hollows in the landscape with shallow fills of sediment overlying the glacial surface. Our vibrocorer can penetrate to ~5-6m depending on the sediments, absence of large cobbles or bedrock, heavy seas and luck. Fingers were regularly crossed and the only wooden items in the all metal BGS vibrocorer cabin are now getting quite worn by us touching them for luck and the right sediments. Broadly we divided the Irish Sea basin into four sub areas, 1. South of a line between the Isle of Man and Barrow-in-Furness completed by 21.30 on 30th July, the deeper waters between the Isle of Man and western Cumbria by 18.30 on 31st July, the Solway Firth (between the Isle of Man and Scotland) by 5am 1st August and finally the deep waters west of the Isle of Man by 11.30am 1st August. >500km of survey line, 34 cores in total, almost all of them reaching the reddish glacimarine muds often laminated some with dropstones and in many cores stiff diamicts with clasts typical in character of Irish Sea glacial tills seen in coastal cliff sections around the basin. We had the sediment contexts we desired, the subglacial to ‘glacimarine’ transition and water-lain ice marginal muds from settings across the transect. The nature of this water-body and answers to the Britice-Chrono geochronological questions must wait on many months of laboratory analysis, but I left the Irish Sea northwards for the Malin Sea and T7, satisfied and with the feeling that the sediments and geophysics alone will fill in a significant and long standing gap in our understanding of the last glaciation of the Irish Sea.

The first of the BRITICE-CHRONO marine transects (transect 4, Celtic Sea) was completed late on Saturday evening. It has been hugely successful – the result of unbelievably excellent weather and sea state, detailed planning and effective delivery by a great team. This has been a controversial and enigmatic part of the British-Irish Ice Sheet for decades with generations of Quaternary geologists attempting to reconstruct glacial events from meagre and sporadic sequences. It was the focus of my PhD back in the early 80’s. A lot of this was spent onshore on the Scillies where the evidence suggested that the Late Devensian maximum advance straddled the northern islands – a conclusion that caused me not inconsiderable grief at the time because large and influential parts of the UK Quaternary community could not accept that the last ice sheet reached this far south. Subsequent work with colleagues using new techniques has supported this original interpretation. I also analysed a series of 12 or so BGS vibrocore samples recovered in the 70’s from the central and southwestern Celtic Sea containing “glacigenic” facies. A northern suite resembling the Scilly Till I interpreted as basal till facies, whereas a southern group – containing spectacular microfossil assemblages – appeared to be glacimarine. On the basis of this available evidence I suggested a mid-shelf grounding line and marine terminus to the Irish Sea Ice Stream. I was unable to explain the origin of some apparently “basal” type diamictons very close to the shelf break; they might possibly be iceberg turbates. More recently I suggested – with additional information from palaeotidal simulations – that the huge Celtic Sea linear ridge bedforms are tidal features reworking the sediments of the terminal ice stream and the Channel River.

Then, starting in the late 2000’s, I became aware that Daniel Praeg from Italy and Steve McCarron from Ireland had become interested in these ridges and were suggesting in conference presentations (e.g. INQUA 2011) that the ridges might actually be subglacial “ giant eskerine” bedforms which, if it were true, would mean that the ice sheet reached right to the shelf break. In Daniel’s model the shelf break diamictons are just that – evidence for shelf edge glaciation. One of the original BGS cores – site 44 – recovered till from the flank of a sand ridge which might suggest that the ridges at least partly pre-dated the glacial event; Daniel, following Pantin & Evans (1984) suggested that the ridges have a carapace of glacigenic sediment and were therefore overridden by ice. But, alternatively, do the glacigenic sediments dive through and under the ridges? A major unanswered question was/is the stratigraphic relationship of the glacigenic sediments to the ridges. There was something faintly ironic in all this: I’d had a lot of grief having argued for an advanced southerly position for the ice sheet, and now here was another team arguing for an even more spectacularly extended southerly limit.

Daniel, with great persistence and motivation, has organised a series of geophysical and coring campaigns with Italian, Irish and BGS colleagues – the last in February-March this year – to attempt to resolve the two models. Spectacularly their last cruise recovered overconsolidated diamicton and normally consolidated glacimarine sediments close to the shelf edge at the southern end of Cockburn Bank (for further details). I won’t steal their thunder because their work is being prepared for publication, but it is fascinating and has injected energy into our researches in this area. Daniel and Steve and colleagues Dayton Dove and my former research student Gill Scott, are now working alongside BRITICE-CHRONO colleagues to help address these questions. Having Daniel as a participant on this James Cook cruise has been a delight and the two hypotheses have been constructively batted to and fro, day and night, with lots of jocular repartee on the nature of things emerging on the sub-bottom profiler; “that’s clearly a buried drumlin”, “no, it’s a proto tidal sand ridge” etc etc.! Were that all scientific controversies were discussed in such a friendly, stimulating and constructive way.

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So, what have we found? Searching for glacigenic sediments in this area is like looking for a needle in a haystick, so aggressive was the subsequent transgressive episode. Much of the sedimentary evidence has simply been eroded (incorporated into sand ridges??!) or buried. The BGS only found glacigenic sediments in 12 cores of the hundreds that were taken. Well, about a third of all our coring deployments recovered glacial or glacimarine sediments, from sites extending from the shelf edge to the Celtic Deep, a total of 14 vibrocores and 5 piston cores. This success is a testament to painstaking preparation – including a reconnaissance geophysical cruise – led by Katrien Van Landeghem, Sara Benetti, Lou Callard and colleagues – so that our targets were well defined. Excellent onboard sub-bottom data has also been crucial, pored over night and day by Daniel, Katrien, Colm, Richard and myself, and the expertise of the BGS and NOC coring teams. There is no doubt that these samples and their contextual geophysical data will transform our understanding of the LGM in the Celtic Sea, a topic that continues to fascinate, bemuse and, occasionally, infuriate. One of our key targets, site 44, stubbornly refused to yield anything but sand – dubbed the “sands of woe” by Lou Callard – that left Daniel, head in hands, muttering “Oh bloody, bloody, hell”!

What about the two hypotheses…well, I already have some modified interpretations emerging – new working hypotheses if you like – but I’m not going to be pushed on these until we have the data analysed from the cores. Having said that, I think Daniel might be partly right and partly wrong, and that I, too, might have been partly right and partly wrong. Such is science!

Dr. Fabio Sacchetti from the Marine Institute (INFOMAR program) has joined the BRITICE-Chrono survey cruise as Irish Observer and multibeam/geophysical support. As Irish Observer Fabio is overlooking survey operation when in Irish water and makes sure that the survey does comply with Irish standard practices. From a scientific point of view, Fabio has spent the last 11 years mapping the seabed offshore Ireland and the last 4-5 years studying its glacial geomorphology. Back in Ireland Fabio works for the INFOMAR program as hydrographic team leader and onboard the RSS James Cook looks after the multibeam and geophysical data acquisition and processing during the night shift.

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So far the collection of good quality multibeam data has been quite challenging for a number of reasons. The ship is equipped with 2 Kongsberg multibeam systems, the EM710 (for shallow to medium water) and the EM120 (for deep water). The data from both systems are routinely collected day and night and they need to be quickly cleaned and tidally corrected in order to be able to create useful bathymetric surfaces. These info are then used for many purposes including geomorphological interpretation, core site selection and ultimately to make sure that the sampling gear are not deployed over risky seabed. At the start of the survey both multibeam systems had to be calibrated in order to provide the best data quality. After few days and with the weather picking up a bit it was also obvious that the motions sensor (which is needed to precisely correct the swath data) wasn’t performing properly. Further modifications to the standard setup had to be done in order to remove motion artefact that were affecting the usability of the data.

3D image of a canyon head used to calibrate the multibeam systems.

Fabio says: so far this has been an exciting scientific cruise simply due to the sheer amount achieved by the scientists and crew aboard the RSS James Cook, especially in light of anticipated challenges posed by the type of glacial sediment required to be cored, which is proving to be incredibly hard to penetrate. Working with some of the best marine glaciologists in Europe is exciting and challenging at the same time. Data are not just collected but analysed and interpreted on the fly and this contributes to a more hectic, clever, and scientific hands on approach, which makes the all survey way more interesting. It is also a pleasure to see how much projects such as INFOMAR can support and help the scientific communities providing top quality multibeam and geophysical data free of charge, which has been fundamental during the planning of this ambitious research project. The RRS James Cook is an exceptionally good platform for survey and sampling operation with top class facilities and lab space. This is an incredible experience and allows me to learn how things are done onboard one of the best research ship in the world.